/etc/prosody/certs/localhost.cert is in prosody 0.9.1-1.
This file is owned by root:root, with mode 0o777.
It is a symlink to /etc/prosody/certs/../../ssl/certs/ssl-cert-snakeoil.pem
/etc/prosody/certs/../../ssl/certs/ssl-cert-snakeoil.pem